Metal diaphragm structure for pressure regulators

ABSTRACT

A metal diaphragm structure for pressure regulators for increasing flow capacity, flow control, and pressure rating. The structure includes a specially shaped metal diaphragm installed and clamped on its periphery into the outlet cavity of a pressure regulator body. The diaphragm is a circular thin metal disc dome shaped with specifically controlled height and thickness values.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. ProvisionalApplication No. 60/345,098, filed Nov. 9, 2001.

BACKGROUND OF INVENTION

[0002] 1. Technical Field

[0003] The present invention relates generally to metal diaphragmregulators. More specifically, the present invention relates to a metaldiaphragm structure for pressure regulators for increasing flowcapacity, flow control, and pressure rating.

[0004] 2. Background Information

[0005] Metal diaphragm regulators have been in use for years. Typically,metal diaphragm regulators include a flexible metal diaphragm clampedbetween a body section, and an actuator section.

[0006] The body section typically has at least one inlet, or highpressure fluid port and at least one outlet, or low pressure orregulated fluid port. A poppet valve, seat, and bias spring aretypically contained within the body section. The poppet valve and seatseparate the high pressure from the low regulated pressure. The biasspring biases the poppet valve against the seat enabling a positivefluid shut-off.

[0007] The actuator section, which usually contains an adjustably loadedcompression spring commonly referred to as a ‘range’ spring, applies adownward reference force upon the upper surface of the diaphragm. Thiscauses the diaphragm to deflect, engaging the poppet valve away from itsvalve seat and allowing fluid flow and pressure to build on thelow-pressure side. The greater the deflection, the greater the poppetvalve opening and corresponding fluid flow. The fluid pressure on thelow-pressure side acts on the underside of the diaphragm applying anupward force. Obviously, the greater the pressure, the greater theupward force.

[0008] As such, the diaphragm's deflection/poppet opening is dictated bya balance-of-forces. The range spring applies a downward force. Thebalancing upward forces are the outlet pressure acting on the diaphragmeffective surface area, the bias spring, the diaphragm or spring force,and the inlet pressure acting on the poppet/seat area. This can beillustrated by the equation

Range Spring Force=Outlet Pressure Force+Bias Spring Force+DiaphragmSpring Force+Inlet Pressure Force

[0009] A problem with conventional metal diaphragm regulators is thatthe diaphragms have a positive spring rate that contributes to areduction in flow capacity. Flow capacity is the usable flow range of apressure regulator without significant loss in outlet pressure. Thehigher the diaphragm spring rate, the greater the reduction in flowcapacity.

[0010] The diaphragm deflection multiplied by the diaphragm spring rateequals the diaphragm spring force. As the diaphragm and poppet valvedeflect downward, not only does flow increase, but also the diaphragmspring force increases, with the amount of change dependent upon itsspring rate. As shown in the above ‘balance-of-forces’ equation, anincrease in diaphragm spring force contributes to a decrease in outletpressure, resulting in a reduction of flow capacity.

[0011] This problem is further exasperated with a small or miniaturemetal diaphragm pressure regulator. Often it is desirable to useminiature metal diaphragm pressure regulators; however, what is notdesirable is the extra reduction in flow capacity associated with thesmaller size. Smaller diametrically sized diaphragms are less flexible,and they therefore typically have higher spring rates.

[0012] Examples of methods to reduce spring rates within a pressureregulator found in the art include U.S. Pat. Nos. 1,103,020 and3,689,055. Although these help to reduce spring rates, they do so byrequiring additional components, added complexity, and increased costs.

[0013] Another problem with conventional metal diaphragm regulators isthat the diaphragm deflection and its associated poppet valve deflectionis very small, particularly with smaller regulators, which limits themetering capability or controllability of the flow. The poppet valve asit deflects into or away from the valve seat changes the annular orificearea, thereby changing the flow. A greater deflection would allow for afiner and more controllable flow from the no-flow to full flow range.This would result in a smoother and more stable pressure control as flowdemands change. To obtain the same flow range with a shorter deflectionwould result in a very ‘coarse’ flow control, resulting in a less stablepressure control.

[0014] Another problem with conventional metal diaphragm regulators istheir low maximum inlet pressure rating. The maximum inlet pressurerating is primarily based on the weakest link, normally the thin metaldiaphragm. Even though the diaphragm is located on the low-pressureside, the diaphragm must be able to hold without rupturing full inletpressure with a suitable safety margin in the event of seat leakage.This is especially true in industries such as the semiconductorindustry, where many of the gases that are pressure regulated areextremely hazardous (toxic, flammable, poisonous, pyrophoric, corrosive,etc.).

[0015] Metal diaphragms currently are designed to be as thin asreasonably possible so as to minimize the above-mentioned problems ofhigh spring rate and short deflection. A thinner diaphragm has a lowerspring rate and is typically able to deflect more. However, thinning outa diaphragm reduces its pressure holding capability.

[0016] While the inventions of the above-mentioned patents may besuitable for the particular purpose to which they address, they are notas suitable for increasing flow capacity, flow control, and pressurerating. Accordingly, there is a need for a metal diaphragm structure forpressure regulators that increases flow capacity, flow control, andpressure rating.

SUMMARY OF INVENTION

[0017] In view of the foregoing disadvantages inherent in known types ofmetal diaphragm regulators found in the art, the present inventionprovides a new metal diaphragm structure for pressure regulatorsconstruction that can be utilized for increasing flow capacity, flowcontrol, and pressure rating. This metal diaphragm structure forpressure regulators substantially departs from the conventional conceptsand designs of the prior art, and in so doing provides an apparatusprimarily developed for the purpose of increasing flow capacity, flowcontrol, and pressure rating.

[0018] The present invention generally includes a specially shaped metaldiaphragm installed and clamped on its periphery into the outlet cavityof a pressure regulator body. The diaphragm is a circular thin metaldisc dome shaped with specifically controlled height and thicknessvalues.

[0019] The present invention further provides a metal diaphragmstructure for pressure regulators that increases flow capacity, flowcontrol, and pressure rating. The present invention also provides ametal diaphragm structure for pressure regulators that produces anon-positive spring rate throughout its usable deflection.

[0020] The metal diaphragm structure for pressure regulators of thepresent invention allows for a large deflection relative to itsdiametric size. The metal diaphragm structure of the present inventionalso utilizes a thick diaphragm material relative to its diametric size.Further, the metal diaphragm structure for pressure regulators accordingto the present invention increases flow capacity, flow control, andpressure rating without requiring additional components.

[0021] There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofmay be better understood, and in order that the present contribution tothe art may be better appreciated. Additional features of the inventionwill be described hereinafter.

[0022] It is to be understood that the invention is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description or illustrated inthe drawings. The invention is capable of other embodiments and of beingpracticed and carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein are for the purposeof the description and should not be regarded as limiting.

BRIEF DESCRIPTION OF DRAWINGS

[0023] Various other objects, features and attendant advantages of thepresent invention will become fully appreciated as the same becomesbetter understood when considered in conjunction with the accompanyingdrawings, in which like reference characters designate the same orsimilar parts throughout the several views, and wherein:

[0024]FIG. 1 is a cross sectional partial view of a pressure regulatorincorporating the present invention.

[0025]FIG. 2A is a cross sectional view showing the present inventionslightly deflected in the no flow condition.

[0026]FIG. 2B is a cross sectional view showing the present inventionfully deflected in the full flow condition.

[0027]FIG. 2C is a graph representing the spring rate (force/deflection)of the present invention.

[0028]FIG. 3A is a cross sectional view showing a typical prior artdiaphragm structure in the no flow condition.

[0029]FIG. 3B is a cross sectional view showing a typical prior artdiaphragm structure in the full flow condition.

[0030]FIG. 3C is a graph representing the spring rate (force/deflection)of a typical prior art diaphragm structure.

[0031]FIG. 4 is a cross sectional view of the present invention.

DETAILED DESCRIPTION

[0032] Turning now descriptively to the drawings, in which similarreference characters denote similar elements throughout the severalviews, the attached figures illustrate a metal diaphragm structure forpressure regulators. The metal diaphragm structure includes a speciallyshaped metal diaphragm installed and clamped on its periphery into theoutlet cavity of a pressure regulator body.

[0033] The diaphragm is a circular thin metal disc dome shaped withspecifically controlled height and thickness values. Referring to FIG.4, the diaphragm 50 is illustrated as being dome-shaped, having aheight, h, and a thickness, t. Element 52 refers to the exterior orupper surface of the diaphragm 50. Element 54 refers to the interior orlower surface of the diaphragm 50. The values of h and t arespecifically determined and held relative to each other so that thediaphragm has a controlled negative spring rate. It has been foundthrough experimentation that, for a set of given conditions, e.g.,diaphragm diametric size, clamping diameter, diaphragm plate contactarea diameter, etc., varying the height to thickness (h/t) ratiocontrols the shape of the spring rate curve.

[0034] At a particular h/t ratio, a sinusoidal spring rate curve can begenerated, as illustrated in FIG. 2C. The downward slope of this curverepresents a negative spring rate. As an example, this particular curvewas generated under a set of given conditions by an h/t ratio ofapproximately 7.8. The deflection range of the negative spring rateshown in FIG. 2C is set as the usable diaphragm deflection range S. FIG.2A shows the start position of the diaphragm deflection, with the poppetvalve 60 in the closed position. In this position, the diaphragm 50 isslightly deflected so that its poppet opening deflection starts in anon-positive spring rate slope. FIG. 2B shows the end position of thediaphragm deflection, with the poppet valve 60 in the full openposition. The diaphragm 50 is deflected so that its deflection isfinished before the spring rate goes positive.

[0035] Too high or too low an h/t ratio is undesirable. For example,using the same set of given conditions, an h/t value larger than 8.2will create an undesirable bi-stable, snap through, oil-canning action,meaning that the diaphragm will snap through and hold in the invertedposition until forced back. An h/t value of less than 7.4 will notgenerate any significant amount of negative spring rate; virtually allof the spring rate will be in the positive direction.

[0036] It is believed that these particular h/t values are specific onlyfor this particular set of given conditions. Varying one or more of theconditions will shift the desired h/t value, which could be foundthrough a trial-and-error approach.

[0037] Ideally, when designing a negative spring rate diaphragm, it isdesirable to start with a thickness sufficient to meet a desiredpressure rating. Then, vary the amount of dome and its height, therebyvarying the h/t value, until the desired negative spring rate isgenerated. This dome shape design allows for a much greater deflectionthan prior-art pressure regulator diaphragms of equal diameters. Thedome shape could be replaced with flat sections so as to approximate thedome radius. FIGS. 3A, 3B, and 3C represent a typical prior artdiaphragm structure and its associated deflection and spring rate curve.

[0038] As shown in FIG. 1, an actuator section 20 threads into aregulator body section 90, loading a clamp plate 40 against thediaphragm 50 in sealing engagement with an edge 98 of the regulator body90. A diaphragm plate 30 is held trapped between the diaphragm 50 and aninterior shoulder 42 of the clamp plate 40. A range spring 10 applies adownward force upon the diaphragm plate 30, pressing the plate 30against the diaphragm 50. The diaphragm 50 is held in contact with adiaphragm plate surface 34 and confined by a diametric edge 36,maintaining a constant surface area contact throughout the usablediaphragm deflection range. A bias spring 80 urges the poppet valve 60into sealing engagement against a seat 70. The diaphragm 50, whendeflected downward by the range spring 10 and diaphragm plate 30,engages a poppet valve tip 62, urging a poppet valve tapered surface 64away from the seat 70. When the poppet valve 60 is in its full upposition, the poppet valve surface 64 sealingly engages the seat 70,holding the diaphragm 50 slightly deflected at the beginning of itsusable deflection range. The diaphragm 50 is placed into position withinthe regulator. If desirable, the diaphragm 50 could be welded orattached by other means at its periphery. Also, the diaphragm 50 and/orthe poppet valve 60 could be physically attached to the diaphragm plate30.

[0039] The range spring 10 is manually compressed and adjusted to setthe desired outlet pressure at an outlet port 94. The range spring forceis exerted upon the diaphragm plate 30, diaphragm 50, and poppet valve60. Referring to FIGS. 2A and 2B, as the diaphragm 50 moves downward inresponse to force changes caused by increased flow demand, the poppetvalve 60 moves downwardly away from the seat 70, allowing fluid to flowfrom the inlet port 92, around the poppet valve 60, through the seat 70,into an outlet cavity 96, and out through the outlet port 94.

[0040] The outlet pressure within the outlet cavity 96 places an upwardforce against the diaphragm 50 creating an upward force. The inletpressure acting on the bottom side of poppet valve 30, i.e., the arearoughly equivalent to the seat area, imposes an additional upward forceon the diaphragm 50. The bias spring 80 also produces an upward force.The outlet pressure will vary accordingly so as to maintain abalance-of-forces. The balance of forces is as follows

Range spring force=Outlet Pressure (acting on diaphragm effective area)Force+Bias Spring Force+Inlet Pressure (acting on poppet seat area)Force+Diaphragm Spring Force

[0041] As the diaphragm 50 and poppet valve 30 deflect in response toincreased flow demand, the bias spring force, diaphragm spring force,and range spring force change with the deflection according to theirindividual spring rates. The net spring rate, determined by thesummation of the individual spring rates multiplied by the deflection,equals the total force change that the outlet pressure must change so asto compensate for and maintain the ‘balance-of-forces’. The range 10 andbias 80 springs both have positive spring rate values. The presentlyinvented diaphragm has a ‘negative’ spring rate value, and when summedtogether with the range and bias spring rates give a lower net springrate value than was the case with prior-art positive spring ratediaphragm. This lower net spring rate value yields a lower force changeper given deflection, yielding a lesser decrease in outlet pressure asflow increases, thereby improving flow capacity.

[0042] It should be understood that the foregoing is considered asillustrative only of the principles of the invention. Further, sincenumerous modifications and changes will readily occur to those skilledin the art, the invention is not to be limited to the exact constructionand operation shown and described. Accordingly, all suitablemodifications and equivalents may be resorted to that fall within thescope of the invention.

1. A pressure regulator comprising: an actuator section for engaging adiaphragm with a regulator body section, the actuator sectionconnectable with the regulator body section; a diaphragm platepositioned between the actuator section and the regulator body section,the diaphragm plate having a constant surface area of contact with adiaphragm; and a poppet valve for controlling flow through the pressureregulator; wherein the diaphragm has a controlled negative diaphragmspring force.
 2. The pressure regulator according to claim 1 wherein thenegative spring rate is controlled by varying the height to thicknessratio of the diaphragm.
 3. The pressure regulator according to claim 1,wherein the diaphragm is slightly deflected when the regulator is in theclosed position, thereby causing the opening of the poppet valve tobegin in a negative spring rate slope.
 4. The pressure regulatoraccording to claim 1, wherein during the opening of the poppet valve,the diaphragm is deflected before the spring rate becomes positive. 5.The pressure regulator according to claim 1, further comprising a clampplate positioned between the actuator and diaphragm, the clamp plate anddiaphragm securing the diaphragm plate within the pressure regulator. 6.The pressure regulator according to claim 1 wherein the diaphragm isdome-shaped.
 7. The pressure regulator according to claim 1, furthercomprising: a range spring having a positive range spring force, therange spring able to apply a downward force on the diaphragm plateagainst the diaphragm; and a bias spring having a positive bias springforce, the bias spring able to apply an upward force against thepoppet/valve in sealing engagement with a seat, thereby closing flowthrough the pressure regulator.
 8. The pressure regulator according toclaim 7 wherein the summation of the range spring force, bias springforce and diaphragm spring force yields a lower net spring rate valuedue to the negative diaphragm spring force.
 9. The pressure regulatoraccording to claim 8 wherein the lower net spring rate value lowers aforce change per given deflection, thereby resulting in a lesserdecrease in outlet pressure as flow increases and improved flow capacitythrough the regulator.